This invention relates in general to portable powered devices, and in particular to a single chip power management unit for providing both power supply and power charging functions.
Portable devices, e.g., cell phones, pagers, laptop computers, personal digital assistants, and the like, require accurate, stable, low dropout regulated voltages to various sensitive load modules in such devices. Such load modules vary with each device, but may include digital loads, analog loads, a reference oscillator, and a real time clock to name a few. Such devices are typically powered by a battery, but may be powered with other voltage sources such as a solar source. Such power sources often provide unregulated voltage. Batteries may provide a voltage source that varies considerably over its useful life and with the amount of load placed on it. When multiple batteries are used in series, such problems are compounded. Thus, the various load modules in such devices cannot operate off direct battery voltage. In addition, such devices also require a battery charging mechanism.
To condition an input voltage source and provide a regulated supply voltage to separate load modules in such devices, a low-dropout voltage regulator (LDO) is typically utilized. LDOs are typically integrated circuits that provide conditioned output voltages over varying loads with minimal voltage dropout over a relatively wide input voltage and operating temperature range. LDOs may provide a fixed output voltage or a varied output voltage. There may also be other circuits to monitor battery voltage and implement functions such as charging the battery. Such power management solutions typically use a larger number of separate integrated circuits for separate functions, which require a large area on a printed circuit board.
Other portable devices may have a power management unit (PMU) including one or more LDOs to condition an input voltage source and provide a regulated supply voltage to separate load modules and to provide other functionality. Such PMUs, however, separate the battery charging function from the PMU function. That is, the battery charger is a separate integrated circuit that uses external transistors, e.g., MOS transistors, to perform the charging function.
Other PMUs may have several LDOs with additional functionality and include a battery charging function. However, such PMUs typically require an external power FET to pass high charging current to the battery. In addition, PMUs that include battery-charging functionality have an input for connecting an AC-DC adapter to charge the battery that cannot be used to supply other external devices with power from the battery. In addition, such PMUs cannot generally work with certain types of AC-DC adapters such as ones that have a pulsing output.
Accordingly, there is a need for a system and method that overcomes the above deficiencies in the prior art and provides a PMU on a single chip for providing both power supply and battery charging functions with improved additional functional features such as battery charge controller functionality, under voltage lockout, start/stop, power on reset, and others.
A PMU consistent with the present invention includes a substrate and a bi-directional pin coupled to the substrate and configured to serve as an input pin during a first condition and as an output pin during a second condition. The first condition may be a charging condition and the second condition may be a supply condition.
A PMU consistent with the present invention may also include a battery charge controller coupled to the substrate. The battery charge controller may have a first charge conductive path providing a first conditioning charge to a battery, and a second charge conductive path providing a second charge conductive path to the battery. The first conditioning charge may be applied to the battery if the output voltage of the battery is below a predetermined full charge threshold level. The first conditioning charge may also be less than the second full charge.
A PMU consistent with the present invention may also include an adapter detector configured to receive a signal representative of the voltage of an external device coupled to the bi-directional pin, and to provide a detector output signal representative of the presence of an adapter. The detector output may provide a positive indication if the adapter is a continuous output adapter or if the adapter is a pulse output adapter. The adapter detector may further include a first detector conductive path configured to receive a signal representative of the voltage of the external device and provide a first detector path output indicative of the presence of a continuous output adapter, a second detector conductive path configured to receive the signal representative of the voltage of the external device and provide a second detector path output indicative of the presence of a pulse output adapter; and an output decision circuit configured to receive the first detector path output and the second detector path output and output a digital one if at least one of the outputs is a digital one.
A PMU consistent with the present invention may also include an under voltage lockout protection circuit configured to prevent start up of the PMU until the voltage of the battery is above a threshold lockout enabling level, and configured to shut down the PMU once the voltage of the battery falls below a threshold lockout disabling level. The threshold lockout disabling level may be set at a lower voltage than the lockout threshold enabling level. The under voltage lockout protection circuit may be further configured to disable the PMU after the voltage of the battery falls below the threshold lockout disabling level for a predetermined lockout delay time.
A PMU consistent with the present invention may also include a plurality of internal switches coupled to a switch conductive path. The switch conductive path may be further coupled to an external switch. The internal switch may be responsive to the external switch allowing the external switch to have multiple functions.
A PMU consistent with the present invention may also include a power on reset (POR) circuit and at least one LDO. The POR circuit may provide a control signal to enable an external controller to start working once at least one LDO has an output voltage that reaches a predetermined LDO voltage threshold level after a predetermined reset time.
A PMU consistent with the present invention may also include a multi-output charge status pin. The multi-output charge status pin may be configured to display the presence or absence of an AC-DC adapter, and an end-of-charge signal.
A method of inputting and outputting power to and from a PMU consistent with the present invention includes connecting an external device to a bi-directional pin of said PMU, triggering a first condition or a second condition, inputting power through the bi-directional pin from the external device during the first condition, and outputting power through the bi-directional pin to the external device from the voltage source of the PMU during said second condition.
A method of detecting an AC-DC adapter coupled to a PMU consistent with the present invention includes receiving a signal representative of the voltage of an external device, providing a positive indication if the adapter is a continuous output adapter, and providing a positive indication if said adapter is a pulse output adapter.
A method of protecting a PMU from entering a start up mode consistent with the present invention includes detecting the voltage of a power source for the PMU, preventing start up of the PMU if the voltage of the power source is below a predetermined threshold lockout enabling voltage level, and shutting down the PMU if the voltage of the power source is below a predetermined threshold lockout disabling voltage level set lower than said threshold lockout enabling voltage level.